Date Code 20010518 Appendix E E-5
SEL-2020 Instruction Manual
RAM Usage Estimation
Of the 512 kbytes of RAM in the SEL-2020, approximately 250,000 bytes are available for
database operations in units without nonvolatile Flash memory; approximately 120,000 bytes are
available in units with nonvolatile Flash memory. To determine the memory used by your
planned functions, sum the memory used for auto-configuration, User region, and Data regions
on each port.
Auto-Configuration Memory Overhead
There is a memory overhead for auto-configuration. In RAM, each configured relay requires:
• Approximately 200 bytes for all relays in Table E.4, except SEL-321-1 and SEL-500
series relays
• Approximately 5000 bytes for newer relays (e.g., SEL-321-1 and SEL-500 series relays)
User Region Memory
Memory requirements for the User region are 30 bytes + twice the USER setting you enter with
the SET A command. (Be aware that the USER setting may automatically increase when you use
the SET M command). If you are using SET M, there will be an additional memory requirement
of 30 bytes per line in your SET M settings.
Data Region Usage
To estimate Data Region (D1 through D8) memory usage for “20” data collection, use the record
sizes directly from Table E.4. For non “20” data collection, you determine the record sizes from
the PARSE and NUM settings:
S=128+NUM if PARSE=CHAR_STRING
S=128+2⋅NUM if PARSE=INT_STRING or PARSE=ASCII_INT
S=128+4⋅NUM if PARSE=ASCII_FLOAT
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